1. Field of the Invention
The present invention relates to a base station, a subordinated station and transmission methods thereof. More specifically, the present invention relates to a base station, a subordinated station and transmission methods thereof complying with an IEEE 802.16 m standard.
2. Descriptions of the Related Art
With continuous advancement in science and technology, people are imposing ever higher requirements on communications. Nowadays, more and more importance is being attached to convenience of communications in addition to requirements on quality of communications. Wireless communications are advantageous in that they provide higher mobility by obviating the need of physical communication network wiring. Therefore, wireless-communication-enabled products such as mobile phones, notebook computers and the like are more and more popular in recent years and have become the mainstream products in the consumer electronics market.
In the conventional wireless networks, there are four kinds of interference types in transmission: data transition in time division duplex (TDD), data transition in frequency division duplex (FDD), the interference in central zone edge, and the interference in cell zone edge.
Particularly, please refer to FIG. 1A, which is a schematic view of a transmission cell 1a in the conventional wireless network. The transmission cell 1a comprises a plurality of central zones 100, 104, 108, a plurality of cell edge zones 102, 106, 110, a base station (BS) 111a, a plurality of subordinated station (SS) 103, 105, 107, 109, 111, 113, 115, 117 corresponding to the BS 101a. First, the interference of the data transition in TDD is described. In the different central zones, if down link (DL) and up link (UL) between the BS 101a and the SSs are operated at the same time, the different SSs may have interference in the data transmission.
The interference of the data transition in FDD occurs in this situation that if the different SSs operate at the same frequency, the SS may receive another SS's signal and get interference. The interference in central zone edge means that if the SS is positioned in the edge of the central zone, it may receive the two kinds of signals from the two different central zones, and one of the signals received by the SS is the interference. For example, the SS 117 may receive the two kinds of signals from the central zones 100 and 104, and one of the signals received by the SS 117 is the interference. Similarly, the SSs 109 and 113 may meet the same interference as the SS 117, and will not be described again.
The interference in cell zone edge means that if the SS is positioned in cell zone edge and the BS's signal power is lower, it may receive another BS's signal to make interference. For example, the SS 107 is positioned in the edge of the cell zone and the BS's 101a signal power is lower, the SS 107 may receive another BS's signal to make interference. Similarly, the SSs 111 and 115 may meet the same interference as the SS 107, and will not be described again.
Moreover, please refer to FIG. 1B, which is a schematic view illustrating the transmission cell 1a and a transmission cell 1b in the conventional wireless network. As shown in FIG. 1B, the SS 111 is within the signal coverage between the transmission cell 1a and the transmission cell 1b. Specifically, the SS 111 is in a cell zone edge of the transmission cell 1a and the transmission cell 1b, and is communicating with the BS 101a of the transmission cell 1a and a BS 101b of the transmission cell 1b at the same time, which often occurs in a handover procedure. However, the SS 111 may receive signals from the BS 101a and the BS 101b meantime, and the interference occurs in cell zone edge accordingly to effect the communication quality.
In summary, the aforementioned interference affects the quality of communications between the BS and the SS in the wireless network seriously. How to reduce the interference in the wireless network efficiently is still an objective for the industry to endeavor.